For a first HPDE? Keep it on. You'll have about 100 other things to worry about and focus on. I look at DSC as more of a learning tool than a crutch for a first timer. Trust me...you can still go off track with DSC on.

But IMO it really depends on your goals. If you have previous car control experience (clinics, auto-x), want to race or have a goal that involves building skills AND you are willing to sacrifice the car then I would say that you really need to turn it off from the beginning. HPDE insurance is never a bad idea...check out BMWCCA for Loctite or something...they have pretty reasonable rates.

If you're there to have fun, keep MDM on. It will scare the crap out of you if you screw up but will keep things mostly in control.

I can say from my owm personal experience, I kept DSC on in my 330 for the longest. This became an issue because you get significantly faster pretty quickly. So by the time I was in the intermediate groups the speed and stakes were a lot higher when I started to plateau because of DSC and the lack of car control skills. If I had just started with it off then I would have made faster progress.

I ended up doing auto-x and a drift event to really learn car control which has been a tremendous help.

One of my goals is specifically to learn improved car control. I'm going to discuss it my instructor and go from there. I'm leaning towards suggesting m-track mode, but we'll see what my instructor thinks.